Power-sharing in Northern Ireland stands on the brink after First Minister Peter Robinson stepped down and the majority of his Executive ministers resigned amid a crisis sparked by a murder linked to the IRA.

Democratic Unionist leader Mr Robinson has asked current DUP finance minister Arlene Foster to remain in the Executive and take over as acting First Minister.

The mass walkout from the mandatory coalition came after the DUP failed to get the Assembly adjourned for a period to allow crisis talks to address the implications of the murder of Kevin McGuigan to take place.

The political furore over the killing intensified on Wednesday when three senior republicans, including Sinn Fein's northern chairman Bobby Storey, were arrested in connection with the murder of Kevin McGuigan. However, all three have been released unconditionally tonight.

As he announced the resignations, Mr Robinson repeated a demand for the Government to suspend the institutions outright to enable space for the talks to happen. Northern Ireland Secretary Theresa Villiers tonight rejected the call.

The fallout from the murder of Kevin McGuigan has already seen the Ulster Unionists resign their one ministerial post.

The exit of Mr Robinson along with three of the DUP's four other ministers, and its one junior minister, has left the 13 minister administration in freefall. The departments of health and social care; social development; enterprise trade and investment; and regional development are now effectively rudderless.

Collapse of power-sharing is not inevitable but its demise appears to have been hastened by a day of dramatic developments at Stormont.

The DUP wanted all Assembly business suspended to allow crisis talks to take place about the political consequences of the murder of Mr McGuigan.

Mr Robinson's announcement came after Sinn Fein, the SDLP and the Ulster Unionists voted against a DUP proposal to adjourn the Assembly.

He issued a resignation ultimatum on Wednesday after the arrest of republicans Mr Storey, Eddie Copeland and Brian Gillen over the fatal shooting of former IRA man Mr McGuigan. Mr Copeland and Mr Gillen remain in custody.

Police have said current members of the IRA were involved in last month's shooting of Mr McGuigan in a suspected revenge attack for the murder of former IRA commander Gerard "Jock" Davison in Belfast three months earlier.

The revelations about the IRA have heaped pressure on Sinn Fein to explain why the supposedly defunct paramilitary organisation is still in existence.

Mrs Foster, a Fermanagh and South Tyrone MLA, is the current finance minister and she will also continue in that role.

Mr Robinson said: "In light of the decision by republicans, nationalists and the UUP to continue with business as usual in the Assembly, I am therefore standing aside as First Minister and other DUP ministers will resign with immediate effect with the exception of Arlene Foster.

"I have asked Arlene to remain in post as Finance Minister and acting First Minister to ensure that nationalists and republicans are not able to take financial and other decisions that may be detrimental to Northern Ireland."

Northern Ireland Secretary Theresa Villiers

Ms Villiers said she would not be suspending the devolved institutions and called on the local parties to come together.

She said the DUP resignations would mean the functioning of the Executive became much more difficult.

"It is a sign of a complete breakdown in working relationships within the Executive," she said.